I did this once when I worked in semiconductor to identify a counterfeit component. The basic process I used was the same as OP: dremel a pocket, slowly drip ni

I did this once when I worked in semiconductor to identify a counterfeit component. The basic process I used was the same as OP: dremel a pocket, slowly drip nitric acid to dissolve the package, and an bath with ultrasonic cleaning. Although I thought we used isopropyl alcohol instead of acetone. It's been a few years so my memory may be incorrect. Looking at dies under a microscope is fascinating, especially if there is anyone around who can help explain what you're looking at. Sort of like exploring an alien robot civilization. :-) In this case it turned out someone had taken one of our competitor's dies (probably a test reject), packaged it, and labeled it as ours. I'm not sure why they bothered with a die at all since it wasn't like it was pin compatible or even functional.